The significant role of dual frames in the progress of Frame theory

For a given frame $$\{\zeta_i\}_{i=1}^\infty$$, any Bessel sequence $$\{\eta_i\}_{i=1}^\infty$$ satisfying in the following identity for every $$\xi\in H$$ $$\xi=\sum_{i=1}^\infty \langle \xi, \eta_i\rangle \zeta_i$$ is called a dual frame associated with $$\{\zeta_i\}_{i=1}^\infty$$.

Q. What are the significant roles of the notion of dual frames in the progress of Frame theory. For example can we say that, if a frame is considered as a coded signal, any associated dual frame is used to decode it?!

Any other suggestion concerning its essential role?